These were the sons of Levi after the house of their fathers; even the chief of the fathers, as they were counted by number of names by their polls, that did the work for the service of the house of the LORD, from the age of twenty years and upward.
These were the children of Levi based on their family leaders. The leaders were determined by counting the names at each family's head. They performed tasks for the Lord's house starting from the age of twenty and above.